Written-in runout due to vibration of the cage of a spindle motor of a disc drive is detected by identifying an initial cage frequency value of the motor. A written-in magnitude of successive servo burst closures, D(nc), is read over a plurality of tracks, and a maximum servo burst closure D(ncp) is identified from the plurality of read servo bursts. A magnitude of the cage frequency at a servo sector n0 is calculated based on a difference between the read magnitudes of the servo burst closures at servo sectors nc and nc+1, and a phase of the cage frequency is calculated based on the magnitude of the written-in cage frequency at servo sector n0. The profile, in the form of cage frequency, maximum servo burst closure magnitude, and initial phase, is stored in a memory or table for each of a plurality of radial zones of tracks. The profile is combined with a position error signal and applied to the controller in a feed forward scheme to adjust the position of the head based on the written-in runout.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A process of identifying written-in runout due to vibration of the cage of a motor that moves a device having sectors comprising steps of: a) calculating a magnitude of the cage frequency at an initial sector; and b) calculating a phase of the cage frequency based on the magnitude of the written-in cage frequency at the initial sector.
2. The process of claim 1 wherein the device is a rotatable medium having a plurality of substantially concentric storage tracks, each track having a plurality of servo sectors, at least some tracks exhibiting a servo burst closure between successive servo sectors due to the written-in runout, the process further comprising: c) reading a written-in magnitude of servo burst closures over a plurality of tracks, and wherein the cage frequency magnitude is calculated based on a difference between the read magnitudes of the servo burst closures.
3. The process of claim 2 , wherein step (c) is performed over successive servo burst closures over the plurality of tracks.
4. The process of claim 2 , further comprising: d) identifying a maximum servo burst closure from the plurality of read servo bursts, and e) storing values of the cage frequency, maximum servo burst closure and calculated phase.
5. The process of claim 2 , further comprising d) identifying a maximum servo burst closure from the plurality of read servo bursts, and wherein the calculation of the cage frequency magnitude at the initial sector comprises: calculating a servo sector having the maximum servo burst closure, and calculating a cage frequency magnitude based on the maximum servo burst closure and a number of servo sectors between the initial servo sector and the servo sector having the maximum servo burst closure.
6. The process of claim 5 , further comprising: e) storing values of the cage frequency, maximum servo burst closure and calculated phase.
7. The process of claim 2 , further comprising: d) identifying a maximum servo burst closure from the plurality of read servo bursts, e) segregating the tracks into a plurality of zones, and f) repeating steps (a) through (d) for each zone.
8. The process of claim 7 , further comprising: g) storing values of the cage frequency, maximum servo burst closure and calculated phase for each zone.
9. The process of claim 7 , wherein the calculation of the cage frequency magnitude at the initial sector comprises: calculating a servo sector having the maximum servo burst closure, and calculating a cage frequency magnitude at the initial servo sector based on the maximum servo burst closure and a number of servo sectors between the initial servo sector and the servo sector having the maximum servo burst closure.
10. The process of claim 9 , further comprising: g) storing values of the cage frequency, maximum servo burst closure and calculated phase for each zone.
11. A process of controlling a movable arm comprising: providing a signal to control the movable arm, the signal being based at least in part on a transduced position signal and a cage frequency profile of written-in cage frequency runout.
12. The process of claim 11 , further comprising: reading the cage frequency profile from a memory, combining the cage frequency profile, a signal representing a position disturbance of the arm, and a position command signal, and applying the combined signal to move the arm.
13. The process of claim 12 , wherein the cage frequency profile is part of a zero acceleration path feed forward to an arm controller.
14. The process of claim 11 , further comprising: modifying the position signal based on repeatable written-in runout, identifying cage frequency parameters, generating the cage frequency profile based on the cage frequency parameters, learning correction parameters for the repeatable runout with a zero acceleration path, modifying the learned correction parameters with the cage frequency profile, and storing the modified correction parameters.
15. The process of claim 14 , wherein the arm is positionable relative to tracks on a medium, wherein each track has a plurality of servo sectors, and the generation of the cage frequency profile comprises: calculating a cage frequency correction signal based on P ci ( n ) = P ci sin ( 2 ( n + n ci ) N ci ) , and n s ( m ) = remainder ( N W m + n s0 N k ) , where P ci (n) is the magnitude of the cage frequency signal at a servo sector, n s (m) is the servo sector where a servo burst closure occurs, P ci is the peak magnitude of the cage frequency signal, n n ci is the burst write time in terms of number of servo sectors of the cage frequency cycle, N ci is the number of servo sectors in a cycle of cage frequency signal, N w is the burst write time in terms of number of servo sectors of a track, m is the number of cage frequency cycles to the track, n s0 is the sector of burst closure in cycle m 0, and N k is the number of servo sectors on the track.
16. The process of claim 14 , further comprising: applying the stored correction parameters to the position signal during movement of the arm.
17. Apparatus for compensating a radial position of a device for written-in cage frequency runout, the device being coupled to an actuator for radial positioning relative to a rotatable medium, the apparatus comprising: a controller providing a signal to the actuator to position the device relative to the medium, the signal being based at least in part on a position signal representing a position of the device; and cage frequency profile means for modifying the signal based on a cage frequency profile of the written-in cage frequency runout, which is associated with the device.
18. The apparatus of claim 17 , wherein the cage frequency profile means includes: a memory storing data representing cage frequency parameters, and a processor responsive to the cage frequency parameters for modifying a signal representing a position disturbance of the device, the controller being responsive to the processor to operate the actuator to control the position of the device.
19. The apparatus of claim 18 , wherein the data stored in the memory represents written-in repeatable runout modified by written-in non-repeatable runout due to cage frequency.
20. The apparatus of claim 18 , wherein data stored in the processor is responsive to the data stored in the memory to interpolate a cage frequency correction signal, the processor further including a summing device for summing the cage frequency correction signal with the signal representing position disturbance of the device.
21. The apparatus of claim 20 , wherein the medium has a plurality of tracks each having a plurality of servo sectors, and the processor is so disposed and arranged to calculate the cage frequency correction signal based on P ci ( n ) = P ci sin ( 2 ( n + n ci ) N ci ) , and n s ( m ) = remainder ( N W m + n s0 N k ) , where P ci (n) is the magnitude of the cage frequency signal at a servo sector, n s (m) is the servo sector where a servo burst closure occurs, P ci is the peak magnitude of the cage frequency signal, n n ci is the burst write time in terms of number of servo sectors of the cage frequency cycle, N ci is the number of servo sectors in a cycle of cage frequency signal, N w is the burst write time in terms of number of servo sectors of the track, m is the number of cage frequency cycles to the track, n s0 is the sector of burst closure in cycle m 0, and Nk is the number of servo sectors on the track.
22. The apparatus of claim 17 , wherein the cage frequency profile means includes a zero acceleration path feed forward to the controller.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
April 27, 2001
August 31, 2004
Browse 5M+ US patents with plain-English claim translations and AI-generated analysis.